1. Field of the Invention
This invention relates to a discharge valve for a compressor, especially a reciprocating type compressor, for use in an air conditioner, refrigerator, freezer and the like to supply a high-temperature and high-pressure gaseous thermal medium to a following stage.
2. Description of the Prior Art
Various types of compressors serve the compression process in a refrigeration cycle which consists of compression, condensation, expansion and evaporation to supply a compresed gaseous thermal medium with high-temperature and high-pressure to a following process, are known, and among these, one to be particularly considered the reciprocating compressor.
Such a reciprocating compressor, as shown in FIG. 1 and FIG. 2, generally includes a motor 10 having a rotator 12 with crank shaft 12A, and a compression device 20 which includes a piston 23 connected to a crank shaft 12A through a connecting rod 22 to enable reciprocating motion of the piston 23 and a cylinder 21 containing the reciprocating piston 23. Positioned on the top of the cylinder 21 is a valve plate 30 with a suction passage 31 and a discharge passage 32. A head 40 encloses valve plate 30.
Suction and discharge valve members 33 and 34 are positioned on the inner and outer sides of the valve plate 30, respectively, to selectively control the flow of thermal medium through the respective suction and discharge passage 31 and 32. The inner space of the cylinder head 40 is divided into a discharge chamber 41 and a suction chamber (so-called, a space formed in the other side of the discharge chamber 41 in FIG. 2 and thus can not be seen) which are isolated from each other by a partition (not shown) and contains the respective suction passage 31 and discharge passage 32.
A reciprocating compressor like this has problems in that the noise due to frictional contacts between the discharge valve members 34 as they perform the discharge and suction process is considerable. Also, the remaining thermal medium in the discharge passage 32 results in a lowered deteriorated compressing efficiency.
With reference to FIG. 2, in suction mode of the compression part 20, the backward motion of the piston 23 closes the discharge passage 32 with the aid of the elasticity of the discharge valve member 34 and the generated moment pressure difference between the cylinder 21 and the discharge chamber 41, while the suction valve member 33 opens the suction passage 31 to initiate the suction stroke for bringing the thermal medium into the cylinder 21. When the piston 23 has reached its maximum travel from the valve plate 30 and initates the compression stroke back toward the valve plate 30, the relative increased pressure in the cylinder 21 and the elasticity of the suction valve member 33 closes the suction passage 31 to end the suction mode.
When the piston 23 has advanced and attained a certain predetermined cylinder pressure, the cylinder pressure forces the discharge valve member 34 against elastic resistance thereof opening the discharge passage 32 and urging the thermal medium in the cylinder 21 into the discharge chamber 41 through the discharge passage 32.
At this time, because the discharge valve assembly 34 consists of a pair of reed type elastic valve seats 341A and 341B, the respective ends of which are bent in an direction opposite to each other, an oppressing plate 342 is placed in parallel manner thereover to keep seats 341A and 341B in position, together with a restrainer 343 and a keeper 344, the slipping friction among the members generates considerable noise.
Moreover, the discharge valve members 341A, 341B, 342, 343 and 344 are mounted at both ends of the valve plate 30 by a pair of fixing pins 345A and 345B. The fixing pins 345A and 345B are parallel and spaced apart from each other with the members 341A, 341B, 342, 343 and 34 superposed one on another therebetween in a vertical arrangement. Thus, when the piston 23 performs the suction mode, the middle part of the valve seat 341A is slightly drawn into the discharge passage 32 by the negative pressure in the cylinder 21 to close the passage 32.
In this type of compressor, there is a problem in that the valve seat 341A, originally having flat reed shape, could not provide complete isolation of the discharge passage 32 and allowed a small amount of backward flow of the compressed gas around the discharge passage 32 resulting in the deterioration of the compressor efficiency.
In the discharge mode, there is also a problem in that the striking contact of the returning valve seat 341A against the valve seat 341B and the vibration of the seats 341A and 341B due to their elasticity and to the discharge pressure from the cylinder 21 were resulted in vibration noises.
In addition to these problems, the complicated construction and difficult assembly of the discharge valve assembly 34 which consists of numerous components caused reliability problems. The inaccuracy in the fixing regions of the fixing pin 345A and 345B for mounting the valve members on the valve plate 30 gave rise to leakage of the thermal medium which also deteriorated of the compressor efficiency.
During the initiation of the suction process, the thermal medium remaining in the discharge passage 32 was mixed with the newly medium drawn therein and then reexpanded. Thus, the energy used to compress this small amount of thermal medium was lost, which added to the lowering of the efficiency of the compressor.
For reducing noise, U.S. Pat. No. 4,537,566 (Aug. 8, 27, 1985) disclosed a valve assembly for a compressor which includes a valve plate having a gas passage extending therethrough, an elongated valve member having a portion overlying the passage and operative to selectively control flow of gas therethrough, resilient biasing device acting on the valve member for exerting a moment thereon, and fastner means extending from the valve plate for retaining the biasing device and the valve member in assembled relation with the valve plate.
However, while this valve assembly achieved a significant decrease in the compressor noise level, but was attended with a slight decrease in operating efficiency.
The problems of the above mentioned leakage of thermal medium in conjuction with the fastner device or fixing pins, and the decrease in compressor efficiency due to gas remaining in the discharge passage reults from the use of reed type valve members were not eliminated.